--- a/mod_muc_limits/mod_muc_limits.lua	Sun Jun 03 01:34:23 2018 +0200
+++ b/mod_muc_limits/mod_muc_limits.lua	Sun Jun 03 13:55:10 2018 +0200
@@ -25,6 +25,18 @@
 	dropped_jids = nil;
 end
 
+local function get_non_outcast_affiliations(room)
+	local nmembers = 0;
+	-- this is an evil hack, we probably should not access _affiliations
+	-- directly ...
+	for _, aff in pairs(room._affiliations) do
+		if aff ~= "outcast" then
+			nmembers = nmembers + 1;
+		end
+	end
+	return nmembers;
+end
+
 local function handle_stanza(event)
 	local origin, stanza = event.origin, event.stanza;
 	if stanza.name == "presence" and stanza.attr.type == "unavailable" then -- Don't limit room leaving
@@ -49,7 +61,15 @@
 		throttle = new_throttle(period*burst, burst);
 		room.throttle = throttle;
 	end
-	if not throttle:poll(1) then
+
+	local cost = 1;
+	-- we scale the cost by the inverse of the square root of the number of
+	-- members; this should effectively raise the limit by a factor of
+	-- sqrt(nmembers)
+	local nmembers = math.max(get_non_outcast_affiliations(room), 1);
+	cost = cost / math.sqrt(nmembers);
+
+	if not throttle:poll(cost) then
 		module:log("debug", "Dropping stanza for %s@%s from %s, over rate limit", dest_room, dest_host, from_jid);
 		if not dropped_jids then
 			dropped_jids = { [from_jid] = true, from_jid };